Eugenio maechese



NITE STATES rrrcno ATENT EUGENIO MAROHESE, OF GENOA, ITALY.

SPECIFICATION forming part of Letters Patent No. 326,760, dated Eleptember 22,1885.

Application filed November 1 1884.

(No specimens.) Patented in Germany September 13, 1884; in England September 23, 1884, No.

12,725, and in Italy October 13, 1884, XXXIV, 309.

To all whom it may concern:

Be it known that I, EUGENIO llIARCHESE, a citizen ofItaly, residing at Genoa, in the Kingdom of Italy, have invented a new and useful Process of Extracting Copper from its Ores, of which the following is a specification.

The practical application of electrolysis to the metallurgy of copper has gone no further than the refining of impure metallic copper. All the processes proposed for the practical electrolysis of ores or regulus have completely failed. The reason thereof is, above all, to be ascribed to the'presence of a great percentage of iron in these materials, (ore or regulus) and the great difficulty, that never was surmounted, of obtaining pure and compact electrolytic copper from anodes or solutions, or both, containing iron in great quantity. Other economical and practical difficulties attended the processes that have been proposed, and in effect no one of these processes has been brought into actual application, although a long time has elapsed since they were proposed. A number of these processes had been proposed on the principle of the electrolysis of sulphate of copper brought beforehand iiito solution, the sulphate having to be ob tained by an acid lixiviation of the proposed materials after they had been submitted to a complete roasting. (Oobleys patent.) In this process the iron sulphate which accompanies the copper sulphate in the solution prepared by means of the roasted materials must be separated by aspecial chemical operation from the copper sulphate before the solution containing this salt could be employed in the electrolytic vessels, (voltameters) N o hint is given how the anodes are to be prepared, and the difficulty attending a special chemical separation of iron in the solution, the impossibility of obtaining a complete roasting of the ore or regulus, and so avoiding the loss of a portion of the copper they contain, along with the great amount of mechanical power required for the dissociation of sulphate of copper when a soluble anode is not provided for, render that process inapplicable in practice. Mr. Elhington, (Elhingtons patent,) who proposed and carried on successfully the refining of impure copper by electrolysis, suggests in his specifications to apply the same process to ores or regulus taken from any stages of the usual metallurgical process, although he declares to prefer blister or pimpied copper-tl1at is, impure metallic copper. In fact, the practical extraction of pure copper from ore or regulus by submitting it to the same process as that of refining cop per, as Mr. Elhington suggests, has never been carried on effectually, because it is not practicable. The iron contained in the ore or regulus, which can amount even to forty or fortyfive per cent., renders the process as suggested by Elhington absolutely impracticable; and it is a well-known fact that even in the electrolytic refining of impure copper which contains but a very small percentage of iron the copper-sulphate solution in the electrolytic vessels must be changed as soon as a sensible quantity of the iron has been converted by electrolytic oxidation into iron sulphate, and new copper-sulphate solution, free from iron sulphate, must be supplied to the electrolytic vessels. The reason thereof is the formation at the anode of the ferric salts, and the reduction of the ferric salts into ferrous salts at the cathode. Such atransformation,which requires a less electro-motive force, goes on in a proportion so much the greater, the greater is the quantity of the iron sulphate in the solution, and along with that phe nomeuon the useful electrolysis of copper subsides proportionally. On the other hand, the copper deposit Wants the compactness and purity that are required for practical purposes.

The process that forms the subject of my present invention obviates all the abovestated difficulties, and its most important result is to obtain pure and compact electrolytic copper from anodes made of regulus containing iron in Whatever quantity and employing coppersulphate solutions containing whatever quantity of sulphate of iron. All ores or regulus or other copper material whatever can also be practically treated by my process. The pres. ence of iron in the anode, which I make of regulus, not only does not hinder the efficiency of the process, but is converted into a powerful economical auxiliary, as the ecouomical feature of my process is the utilization of the iron contained in the anode for electrolytic dissociation ofithe sulphate of copper contained in the solution extracted from the roasted ores or regulus. It is well known that the sulphate of copper requires for dissociation an electro-motive force of 1.2 volt in my process by the oxidation of the iron sulphide of the anodes which takes place by theelectric current, a large portion of that electro-motive force is gratuitously supplied, and the electrolysis goes on, practically requiring no more than 0.4 to 0.5 volt for the chemical dissociation and deposition of copper on the cathode. As for the correspond ing difficulty arising in the proposed processes from the presence of large quantities of sul-' phate of iron in the solution,this is completely obviated in my process by means of a contin ually-active circulation of thesolution from the electrolytic vessels to the tanks in which the roasted material is submitted to lixiviation.'

My process for extracting chemically-pure copper by electrolysis from copper ores, copper regulus, or other copper materials is practically carried on thus: The copper ore or copper regulus, or other copper material from which the copper has to be extracted, whatever be the proportion of iron it happens to contain, is roasted in kilns or other suitable extracted by lixiviat-ion,as sulphate of copper,

(and sulphate of iron.) If that residual part of the lixiviation be not sufficient to afford the quantity of anodes required by the process, a convenient portion of the ore or regulus is added accordingly. The economy of the process consisting in availing oneself of the.

iron contained in the anodes for the electrolysis of the copper contained in the solution, there must be a consequent relationbetween the quantity of iron contained in the anodes and the quantity of copper that ought to be regulus containing, say, thirty-five per cent.

of copper and forty per cent. of iron, one hun dred parts of that regulus cast into anode-plates will dissociate approximately 40 X n cal equivalents of copper and iron. case nearly one-third of the regulus that I have to treat must be reducedin form of anodes, and the other two-thirds into solution. An

analogous calculation can be made in every case; also, in order to make the anodes for the process, I take the residue of the ore or regulus, whether alone or with addition of a portion of ore or regulus, or I may use only the ore or regulus, if the residue of the roasted material should be inconvenient for that purpose. The way I make these anodes is by smelting the materials above mentioned (residue of roasting. or ores, or regulus, or a mixture of them),in a cupola-furnace or other furnace, casting thesmelted metallic product (copper, iron. and sulphur, composing the cop per regulus) into cast-iron molds having the dimensions suitable for my plant-say, two feet six inches wide, two feet six inches deep, and one and three-sixteenths inch to one and ninesixteenths inch thick. In the cast-iron mold, which is set vertically on the ground, a small band or wire. of copper is held in suspension during the casting of the smelted regulus, which after the cooling of the plate remains In this inserted in it,=andaffords an easy means for connecting the anode to the general copper conductors of the electric current when it is placed into the electrolytic vessel or voltame ter. If in the casting of the anodes, as above described. there are any defects, they are broken up and passed into the roasting operation with the ores or regulus intended for the formation of solution and sulphuric acid, as was hereinbefore said, so that not-hing of the material is lost or has to be put aside. The anodes so obtained I place in suitable vessels or voltameters, each of them containing, say, fifteen or twenty anodes. vertically, repose on two longitudinal pieces of wood placed on the bottom of the voltameter, so that between the under side of the anodes and the bottom of the voltameter a certain space (say, six inches high) remains free. To hold the anodes in their upright position and at a fixed distance, I place two wooden racks in the voltameter, between whose teeth the sides of. the anodes are confined. The connection of the anodes with the copper conductors of the current is then made by the cop per band or wire inserted in them. Between the anodes are placed the cathodes of electrolytic copper in communication with the con ductors of the other pole, as is well known. The distance between anodes and cathodes I make about two inches. The solution that-is to operate in these vessels or voltameters so provided withtheir anodes and cathodes I provide, as above said, from the roasted material (ore or regulus) by means of acid solution and lixiviation. The required sulphuric acid is produced in the lead chambers from the sulphur contained in the roasted materials inthe usual way, and. I take the first chamber sulphuric acid. As the ore or regu- 1 lus contains more sulphur than is necessary to IIO sulphatize theiron of the anodes, and as by roasting a large portion of the oxidized iron addition of sulphuric acid in the lixiviatingtanks, so as to maintain the solution but slightly acid. It is by no means required in my process that the lixiviation be complete and absolute. The residue I pass to the smelting ofthe anodes; and to avoid the possibility ofloss of copper oxide I have only to add in the smelting some copper pyrites or iron pyrites. It is not required for the success of my process that the solution be saturated with coppersulphate. In fact, if it contains from one to two per cent. of copper, the proportion is quite sufficient. As to iron sulphate, the solution may, without inconvenience, contain any quantity. In fact, during the process the solution will be always charged with sulphate of iron so far as no physical inconvenience (crystallization of the salt) arises for its circulation.

The main features of my process, in what concerns the solution, is that the solution must continually circulate from the electrolytic vessels or voltameters, where the electric dissociation takes place, to the lixiviation-tanks, where the roasted materials are submitted to the acid action in order to 'sulphatize and so to dissolve the oxides of copper and iron. This circulation can be arranged in different ways and by known means. The sole essential point is that it shall take place continually in each electrolytic vessel or voltameter, and that the so circulating solution, after having passed through one, or a number of the voltameters, be carried to the lixiviation'tanks, to be passed back from there to the voltameters, and so on continually. WVhen the electric current passes into the voltameter so disposed, and does its work of electrolysis, the copper of the anode is dissociated from sulphur and deposits in the cathode. At the same time the iron of the anode is dissociated equally from sulphur and converted into sulphates, the electro-motive force arising from that chemical combination being employed in the dissociation of the sulphate of copper contained in the solution, with deposit also of copper on the cathode. Consequently the solution is gradully impoverished in sulphate of copper, and one of the objects of the circulation is to bring the impoverished solution into the liXiviation-tanks in order that it can appropriate copper sulphate again and regain its original percentage of copper. This fact gives the practical means of arranging the mode of circulation. If the normal solution held, say, three per cent. copper, it can flow through a number of voltameters until'it is reduced to, say, one and a half percent. before being carried back to the lixiviatingtanks. Another object of the continuous circulation is that of maintaining the ferricsalts and the ferrous salts in such a state of admixture in the solution passing through the voltameters as to hinder the dissociation of ferrous salts which could take place, and the consequence of which (the solution being slightly acid) would be a development of hydrogen at the cathode, and the consequent deposition of copper not in a solid and compa ct state, as in galvano -plastic, but'disintegrate and pulverulent, so as to fall down on the bottom of the voltameter. On the otherhand, the immobility of the solution would give rise to the fact that the electric current would become specially absorbed by the reduction of the ferric salts, into ferrous ones instead of being employed exclusively in effecting the dissociation ofthe sulphides of the anodes and of the sulphates of the solution, with the consequent useful deposition of good electrolytic copper on the cathode. A good circulation to that effect I have obtained when about one-fifth of the solution contained in the voltameter passes through it by circulation during one hour. The copper I leave to accumulate on the cathode till it reaches sufficient thickness,as usual in the electrolytic refining of impure copper. The residues of the anodes, in which the sulphur that was first combined with copper and iron remains in the metalloid state, (so that it can burn like sulphur) when they are so impoverished in metals that they are no longer effectual for the proper passing of the electric current, are taken away and passed into the roasting operation with the raw materials, (ore or regulus.) Thus nothing is lost of the copper they might still contain, and the metalloid sulphur contained affords an excellent material for sulphuric acid in the roasting operation. Naturally, if the materials (ore or regulus) contain even very small quantities of precious metals, those metals accumulate gradually in such residual parts,which. become continually richer until they can pass conveniently to a desilvering process. As the solution, circulating as above stated, takes continuallya certain quantityof iron from the anodes, (and from the roasted material,) a portion of the same solution, calculated on the daily increase of the iron sulphate so formed,must be daily brought out of the process. This portion is deprived of the copper contained by the known processes, or by a special electrolysis, where the copper falls on the bottom of the voltameter. The sulphate of iron can be crystallized if there be a convenient sale for it. Otherwise it is thrown away. As to the electrical arrangement, it can be carried on in different known ways. Owing to the practical difficulty of possessing good dynamos having a very small electro-inotive force, I dispose a series of voltameters in tension,so that for every ICC IIO

Volta-meter an eleetromoti-v',e force of about one yoltbe available between the anodes and the cathodes. A n electro-m'otive' force of about,0.5 volt is necessary for the chemical dissociation, and the more that is given depends upon the plant employed. With large surfaces a saving in electro -motive power, and

consequently in mechanical power, can be effected; but the electromotive force must never go below the chemical reaction, which can be measured in every case, Above that required for such reaction the augmentation of the electromotive force corresponds to a restriction of the surfacesth-at is, of the plant of the process. However, too' high an electrorn'iot-ive force, besides being uneconomical, has very great inconveniences, as it can give rise to higher chemical reactions, which could 'produce polarization with very bad consequences.

In all cases in copper e'lectro-metallurgy the.

electro-xjnotive force'of one volt'between anodes and cathodes should be considered as a maximum not to be surpassed.

Having thus "described the nature of my inention and the best means I know of carrying it into effiect, I claimf w The herein-described process for thee'lectrolytical extraction of copper from ores or regulus containing iron, which consists in smelting a portion of the ore or regulus and casting it into plates androasting and liiriviating the other portion,and subjecting the plates to the action of the solution of sulphate of iron and sulphate of copper and an electric 

